Title: Arcing and Next Generation Electrical Airplane Power Hazard Abatement
State of the art – Background New aircraft designs are implementing 230 volt variable frequency AC and 270-540 volt DC electrical power systems to enable the More Electric Aircraft (MEA) concepts. The risk of high energy faults and electrical hazards in these higher voltage systems is increased, thus
the ability to detect and isolate electrical faults is critical to the MEA.
Eaton is the world leader in arc fault protection technologies with over 100 related patents, over
250,000 recorded flight hours with Eaton arc fault protection components. Eaton is the only manufacturer qualified to the SAE AS5692 General Specification for Arc Fault Circuit Breakers.
The conventional 120VAC 400Hz aircraft electrical bus is evolving to a variable frequency system to allow elimination of the complex and heavy constant velocity gearbox generator drives from the engines. While this reduces the weight and
maintenance burdens, it does not improve the ability to efficiently distribute power over the fixed frequency system. New designs from Airbus and Boeing are beginning to implement 230 volt variable frequency AC and 270-540 volt DC electrical power distribution systems to enable the MEA concepts.
Objectives Eaton objectives were to develop arc fault detection modules for 270-540VDC and 230VAC aircraft systems. The characterization of arcing faults through computer modelling, empirical testing and data acquisition of fault voltage and current signatures forming a significant part of the project activity. Arc fault test procedures and apparatus were planned to be designed so as to replicate arcing faults representative of what could occur in an actual aircraft.
The ability of the algorithm design to resist ‘Nuisance tripping’ was planned to be assessed against existing electrical loads.
Arc detection algorithms development was planned using computer based analysis and modelling. The project included the building of Arc fault detection modules to implement the algorithms. These prototype modules were planned to be integrated into a power distribution system.
Finally, the Eaton team planned provided technical support for the field testing and verification of the integrated AFD/switching device solution.
Description of work The project was formed by four main Work Packages:
The Arc Fault Environmental Study
This package involved the setting up of test facilities to enable the production of arcs and capture of the associated characteristics. This work dealt with the capture of information for both High Voltage Alternating Current (HVAC) and High Voltage Direct Current (HVDC) cases. This work was complimented by analytical assessment of some of the test cases for the purpose of developing confidence in modelling methods.
Two types of detection module were produced, one for HVAC and another for HVDC applications. These modules were designed to achieve a Technical Readiness Level 5 (TRL 5) level of development. This provided a “high fidelity” laboratory integration of components within a test bench type of enclosure.
Validation of the Detection Modules
The modules were assessed under test for their response to generated arcs. SAE standard AS5692 was used as the criteria for successful operation of the modules. The resistance of the modules to ‘Nuisance tripping’ is vital. The modules were operated in-line with several available typical aircraft loads to assess the ability of the modules to not react to normal electrical noise.
Integration and Support of Supplied Modules
The validated modules were supplied to the project lead partner. This also included initial commissioning within the new Power Distribution System.
b) Environmental benefits The development of 540VDC and 230VAC Arc
Fault Circuit Interruption (AFCI) technology will facilitate the development of an integrated electrical power distribution system by providing the required high voltage switching components with the technology to reduce the incidence and severity of damage, fires, and electrical defects caused by aging wire insulation that risks aircraft/crew safety. The use of these higher voltage systems will potentially reduce the aircraft weight and fuel consumption. By using higher voltages, current can be significantly reduced whilst still providing the same power and significantly reducing the weight of the wiring as smaller gauge wire is used.
c) Maturity of works performed The work undertaken represented the initial activities under the new higher electrical power conditions. The significant test work conducted to characterise arcs revealed the practicality of conducting such tests. At the point that the project was conducted aerospace facilities for testing at the new power levels were scarce. Test set ups for conducting arcing at the higher power levels are likely to require considerable facilities investment to afford remote operation and safety.
The delivered modules are considered to have achieved a TRL5 level of maturity for HVAC and HVDC arc fault detection.